In the related art, there is known a substrate processing apparatus which includes a processing container that processes a substrate, a boat that holds the substrate, a cover unit that opens or closes a furnace opening provided in the lower end of the processing container, and a lifting mechanism that raises the boat and the cover unit together to carry the boat into the processing container and to press the cover unit onto the furnace opening. In such a substrate processing apparatus, a seal member such as, for example, an O-ring is attached to the cover unit such that the lower end of the processing container and the cover unit are sealed via the seal member when the boat is carried into the processing container.
However, in the substrate processing apparatus, after the substrate is processed, the cover unit descends and the boat is carried out of the processing container by the lifting mechanism.
As a method of carrying the boat out of the processing container, there is known a method of performing a control such that the descending speed of the boat before the seal member is separated from the lower end of the processing container slower than the descending speed of the boat after the seal member is separated from the lower end of the processing container (see, e.g., Japanese Patent Laid-Open Publication No. 2005-056905). According to this method, the vibration of the cover unit, which is generated in the initial stage of lowering and carrying the boat out of the processing container, is suppressed.